LASIK (Laser-Assisted In Situ Keratomileusis) is a surgical procedure that reshapes the cornea to correct common refractive errors like nearsightedness (myopia), farsightedness (hyperopia), and astigmatism. While effective, LASIK has specific limitations and cannot correct all vision problems. Understanding these boundaries is important for individuals considering the procedure.
Vision Issues Beyond Corneal Reshaping
LASIK modifies the cornea’s shape to focus light on the retina. It cannot address vision problems originating from other eye parts or the brain’s visual processing.
Presbyopia, often called age-related farsightedness, is a common condition LASIK does not typically treat. It develops as the eye’s natural lens hardens and loses flexibility with age, making close focus difficult. While some advanced LASIK techniques, like monovision, aim to compensate, traditional LASIK does not reverse these lens changes.
Amblyopia, or “lazy eye,” is a condition LASIK cannot directly fix. It occurs when the brain favors one eye, leading to reduced vision in the weaker eye despite no structural damage. This neurological issue involves the brain-eye connection, not the cornea’s shape. While LASIK might correct a refractive error, it cannot restore the brain pathways for visual processing.
Strabismus, or “crossed eyes,” involves eye misalignment due to muscle imbalance. Since LASIK only reshapes the cornea and does not affect eye muscles, it cannot correct strabismus. If caused by a significant refractive error, LASIK might reduce misalignment, but it is not a primary treatment for the muscle imbalance.
Underlying Ocular Health Conditions
LASIK improves how light focuses on the retina but does not treat or prevent underlying eye diseases. Individuals with certain pre-existing conditions are generally not suitable candidates, as the procedure won’t improve vision loss caused by these diseases.
Cataracts, a clouding of the eye’s natural lens, cannot be treated by LASIK. LASIK reshapes the cornea, but cataracts affect the internal lens, requiring separate surgery to remove and replace it. LASIK does not cause cataracts, but they can develop naturally with age.
Glaucoma is a group of diseases that damage the optic nerve, often due to elevated intraocular pressure. LASIK does not treat glaucoma or prevent its progression. In some instances, the suction applied during LASIK to create the corneal flap can temporarily increase eye pressure, which might be a concern for individuals with pre-existing glaucoma or those at high risk. Patients with well-controlled, early-stage glaucoma might still be candidates, but careful evaluation is necessary.
Macular degeneration affects the macula, the retina’s central part responsible for sharp vision. LASIK cannot repair retinal damage or improve vision loss from it. Similarly, diabetic retinopathy, a diabetes complication damaging retinal blood vessels, is not addressed by LASIK. While LASIK can correct refractive errors in well-controlled diabetic patients without significant eye complications, it won’t resolve existing retinal damage.
Structural and Stability Limitations
Even for common refractive errors, certain eye characteristics or vision fluctuations can make LASIK unsuitable. These are crucial candidacy considerations.
Extremely high prescriptions limit LASIK, as the procedure removes or reshapes corneal tissue. There are practical limits to safe tissue removal without compromising corneal integrity. FDA-approved ranges typically include nearsightedness up to -12.00, farsightedness up to +6.00, and astigmatism up to 6.00 diopters. Correcting beyond these levels risks excessive tissue removal, potentially leading to complications like irregular healing, reduced vision, or ectasia (corneal bulging).
Corneal thickness is a significant structural factor. A minimum thickness is necessary for LASIK to ensure sufficient residual tissue after reshaping. Thin corneas increase complication risk, including ectasia, which can worsen vision. Average corneal thickness is 520-540 microns; many surgeons require at least 500, and some avoid LASIK for corneas less than 470. Tissue removal varies with prescription, generally 12-15 microns per diopter, plus 90-120 microns for the corneal flap.
Unstable vision is a contraindication for LASIK. Vision must be stable for at least one year before the procedure for predictable, lasting outcomes. Hormonal fluctuations (e.g., pregnancy, nursing) can cause temporary vision changes, making outcomes unpredictable. Certain medications or progressive eye conditions also lead to fluctuations. If a patient’s prescription is still changing significantly, LASIK may not provide stable long-term correction.